This commit implements support for publishing MCP servers to GitHub
Container
Registry (ghcr.io) in addition to the existing Docker Hub support,
addressing
Docker Hub rate limiting concerns as requested in #393.
Key changes:
- Add RegistryURLGHCR constant for https://ghcr.io
- Refactor OCI validation to support multiple container registries with
extensible RegistryConfig system
- Implement registry-agnostic authentication system that handles:
- Docker Hub token-based authentication via auth.docker.io
- GHCR token-based authentication via ghcr.io/token service
- Update Accept headers to support OCI image indexes for multi-arch
images
- Extract helper functions to reduce cyclomatic complexity and improve
code maintainability
- Add comprehensive test coverage for both Docker Hub and GHCR scenarios
- Include real image testing with github/github-mcp-server and
nkapila6/mcp-local-rag
- Update publishing documentation with GHCR examples and authentication
details
The implementation maintains backward compatibility with existing Docker
Hub
usage while providing a future-proof architecture for adding additional
container registries. All authentication is now handled through proper
token
services for both registries.
Fixes#393
## Motivation and Context
Docker Hub rate limiting has been causing issues for the MCP registry
when validating OCI images. Adding GHCR support provides an alternative
container registry that many MCP server authors are already using,
reducing the load on Docker Hub and providing more options for the
community.
## How Has This Been Tested?
- All existing unit tests continue to pass
- Added comprehensive test coverage for GHCR scenarios including:
- Non-existent images (proper error handling)
- Real images without MCP annotations (github/github-mcp-server)
- Real images with proper MCP annotations (nkapila6/mcp-local-rag)
- Registry URL validation for both supported registries
- Tested authentication flow manually using curl commands
- Verified multi-arch image support with OCI index manifests
## Breaking Changes
None. This is a purely additive change that maintains full backward
compatibility with existing Docker Hub configurations.
## Types of changes
- [x] New feature (non-breaking change which adds functionality)
- [x] Documentation update
## Checklist
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [x] My code follows the repository's style guidelines
- [x] New and existing tests pass locally
- [x] I have added appropriate error handling
- [x] I have added or updated documentation as needed
## Additional context
The implementation uses a RegistryConfig struct to abstract
registry-specific details like API endpoints, authentication URLs, and
token services. This design makes it straightforward to add support for
additional container registries in the future (such as AWS ECR, Azure
Container Registry, etc.) by simply adding new cases to the
getRegistryConfig function.
The authentication system properly handles the different token services
used by each registry:
- Docker Hub: auth.docker.io with service=registry.docker.io
- GHCR: ghcr.io/token with service=ghcr.io
Both registries now support the full OCI specification including
multi-arch images via OCI image indexes.
<!-- Provide a brief summary of your changes -->
## Motivation and Context
<!-- Why is this change needed? What problem does it solve? -->
The following PR:
* Adds the Transport Type property to Packages. _Even though most
packaged MCP servers are stdio this is not always the case so it's nice
to have the option to specify this for clients._
* Adds a constant for the "stdio" type
* Renames the "streamable" one to "streamable-http" (matching better how
the spec refers to it)
* Updates the seed.file to reflect these changes
## How Has This Been Tested?
<!-- Have you tested this in a real application? Which scenarios were
tested? -->
Locally
## Breaking Changes
<!-- Will users need to update their code or configurations? -->
No
## Types of changes
<!-- What types of changes does your code introduce? Put an `x` in all
the boxes that apply: -->
- [ ] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update
## Checklist
<!-- Go over all the following points, and put an `x` in all the boxes
that apply. -->
- [ ] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [ ] My code follows the repository's style guidelines
- [ ] New and existing tests pass locally
- [ ] I have added appropriate error handling
- [ ] I have added or updated documentation as needed
## Additional context
<!-- Add any other context, implementation notes, or design decisions
-->
This was discussed in
https://github.com/modelcontextprotocol/registry/discussions/200
---------
Signed-off-by: Radoslav Dimitrov <radoslav@stacklok.com>
<!-- Provide a brief summary of your changes -->
## Motivation and Context
<!-- Why is this change needed? What problem does it solve? -->
The following PR updates some of the hardcoded references to public
constants.
## How Has This Been Tested?
<!-- Have you tested this in a real application? Which scenarios were
tested? -->
Locally
## Breaking Changes
<!-- Will users need to update their code or configurations? -->
No
## Types of changes
<!-- What types of changes does your code introduce? Put an `x` in all
the boxes that apply: -->
- [x] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update
## Checklist
<!-- Go over all the following points, and put an `x` in all the boxes
that apply. -->
- [ ] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [ ] My code follows the repository's style guidelines
- [ ] New and existing tests pass locally
- [ ] I have added appropriate error handling
- [ ] I have added or updated documentation as needed
## Additional context
<!-- Add any other context, implementation notes, or design decisions
-->
Signed-off-by: Radoslav Dimitrov <radoslav@stacklok.com>
